Technical Field
This disclosure generally relates to pressure sensors and more particularly to encapsulated pressure sensors for determining a change in pressure due to an applied external force.
Description of the Related Art
Force sensors are commonly utilized in a wide variety of applications. Such force sensors commonly include piezoresistive strain gauges, such as semiconductor strain gauge or metallic strain gauge types. These types of force sensors have certain undesirable issues. For example, semiconductor strain gauge force sensors offer high precision, but are relatively large. Metallic strain gauge force sensors, on the other hand, can be made compact, though this comes with diminished sensitivity. Further, power consumption is an issue with many applications utilizing conventional force sensors.
One application for force sensing is an active stylus or “smart pen,” which are commonly used in connection with a host electronic device, such as a tablet computer or smartphone. Such styluses typically use force sensors to assess or measure the amount of pressure a user applies on the pen. This solution is expensive and not very accurate, as conventional force sensors of the size desirable in a stylus are not particularly sensitive to relatively low forces. Ideally, a force sensor in such an application would be able to detect forces applied to a tip of the stylus in the range of 0-300 grams; however, this is often not possible or not effectively achieved through conventional force sensors used in such styluses. Detection of such low forces would allow an active stylus and host electronic device to more accurately mimic the use of, as one example among many, a very light marking with a pen or pencil.
There is thus a need for improved force sensing devices in this, as well as a variety of other, applications.